"If you're rational and reasonable, it's impossible to discount all these sightings," says author Linda Zimmermann, whose latest book, "Hudson Valley UFOs: Startling Eyewitness Accounts from 1909 to the Present," continues where her first book, "In the Night Sky: Hudson Valley UFO Sightings from the 1930s to the Present," left off — and there's a third book in the works, too. "I've spoken to police officers, physicians, politicians, educated people with no advantage for them whatsoever to tell these stories, especially with the stigma attached to UFO sightings."

Zimmermann, who lives in Chester but grew up in Rockland County, had a sighting about 35 years ago while she was a college student majoring in chemistry and English literature.

She was studying for a test in Nanuet when a friend, who spotted three lights in a triangular shape, called Zimmermann outside. Recalling a Frank Edwards book from her childhood that recounted the sighting of a classic flying saucer over a lake in nearby Harriman State Park, she suggested that they drive there. The hunch paid off as they subsequently witnessed the three lights come together in a blinding blue flash.

But it wasn't until years later, while lecturing about local history for Rockland County's Bicentennial Celebration in 1998, that conversations started taking an otherworldly twist and her interest piqued skyward. She surmises it was the Native American legends that then prompted requests for ghost stories.

"I had one, and then people started calling me, even mailing me keys to check out a haunted house. Using my scientific background, I'd search the history of the old houses," Zimmermann says.

After local history lectures came to include ghost stories, she'd then regularly be approached by people with UFO tales to tell.

"I guess they assumed I did all things strange," she says. "It amazed me, the number of people who had sightings."

And it was those undeniable numbers that led to the birth of her first book, "In the Night Sky," incorporating 15 years worth of stories she collected. Zimmermann discussed her book at last year's Pine Bush UFO Fair — a full day of festivities and events, including a parade, all with a UFO undercurrent.

Because her talk generated so much interest, she'll be speaking twice at Saturday's UFO Fair, again discussing predominately local eyewitness accounts, which continues in her second book. "Hudson Valley UFOs" also includes newspaper archive research that reveals sightings in 1909 of "mysterious air ships at night."

"This is extremely important," she says of the sightings that took place long before man had the capability to fly at night. "Many people credited the Wright Brothers or Edison (with what they saw)."

Along with how early and how many sightings have been documented, Zimmerman is also stunned by how many people have reported being abducted.

"It turned out to be my biggest chapter," she says. "A person typically recalls seeing a UFO — and then it's four hours later. "» The earliest was a 1929 abduction of a little girl in a brightly lit craft with short beings. She was returned several hours later."

Emotions range from elation to terror at sightings, in which different types of crafts are described, leading Zimmermann to suspect different "manufacturers," or points of origin. Similarly, abductees also report myriad emotions.

"The unnerving part for me is speaking to people with that haunted look in their eyes. I can feel the truth," says Zimmerman, whose Facebook page lists the allowed location to park and sky-watch, in the vicinity of Ward Avenue and County Route 17. "Not everyone is credible, but the credible ones make your spine tingle."

Another pattern Zimmermann has noted through the years is that sightings tend to span the generations in particular families.

"It's like one big lab experiment," she says. "One woman who spoke to me was in her 80s and experienced a sighting in 1937, as did her whole family. 'I didn't ask for this to happen to me,' she told me. And her words apply to almost everyone who's had the courage to talk to me. 'But I know what I saw. And I don't appreciate people telling me I'm crazy.' "